In its weekly credit outlook, the credit-rating agency Moody’s Investors Service cautioned on Thursday that more shutdowns could follow.

“The pending closure is credit negative for a small subset of the higher-education sector with similar attributes to Saint Paul’s and other closed colleges: very small, private colleges with a high reliance on student charges, indistinct market positions, and limited donor support,” Moody’s analysts said. “We anticipate more closures for these types of colleges given the current pressures on all higher-education revenue sources and increased accreditation scrutiny.”

A 2012 analysis of nearly 1,700 public and private nonprofit colleges by the consulting firm Bain & Company found that a third of the institutions had been on an “unsustainable financial path” and that an additional 28 percent were “at risk of slipping into an unsustainable condition.”

Nonetheless, closures of traditional four-year colleges remain rare, Moody’s said, with just three in the 2012 fiscal year. But the agency noted a troubling rise in such incidents over the past four years.

Moody’s reports are available to its subscribers only.

Last week at the Summer Seminar, a higher-education conference organized in Minneapolis by the admissions and marketing consultants Hardwick-Day and the Lawlor Group, a Moody’s analyst commented on predictions about impending college closures and a “bubble” in the higher-education market.

“We don’t believe that there is a bubble,” said Eva Bogaty, a member of the Moody’s higher-education and not-for-profit team. The higher-education sector went through the “baby bust” two decades ago, and a number of pundits predicted then that scores of colleges would go out of business. In the end, just one-half of 1 percent did.

Ms. Bogaty ascribed that fact to a fundamental demand for higher education, as college degrees are still connected to stronger earnings and better job prospects.

She noted, however, that the news media have focused on rising costs among colleges and debt among students—usually in articles that are far out of proportion with reality—and that predictions of the vulnerability of colleges are coming back.

“We are not saying that colleges are going out of business like gangbusters,” she said. But the environment has changed, with limited prospects for tuition-revenue growth, strained nontuition-revenue sources, rising debt burdens among students, and a longstanding decline in the buying power of Americans.

In 2007, Moody’s issued 29 ratings upgrades in the sector; in 2012, it issued only two. Ms. Bogaty showed a graph that charted a steep decline in private colleges’ operating revenues against fairly steady spending by the colleges.

“It is really interesting that in 2010—the worst of it for universities—less than 30 percent of private universities cut expenses,” she said. “I’m interested to know if we looked at corporate, what would that be? It wouldn’t be less than 30 percent.”

She argued that colleges needed to find more efficiencies, and that some should consider mergers and sharing services. “That is going to be a wave of the future,” she said.

She also mentioned faculty members. “The elephant in the room is obviously faculty and the shared-governance structure,” Ms. Bogaty said. “How do you deal with that? There is no way that you can operate in the environment that we are in without a major shift in that shared governance.”